1. Field of the Invention
The present invention relates to the use of fungal mycelium as a biopesticide. More particularly, the invention relates to the control and destruction of insects, including carpenter ants, fire ants, termites, flies, beetles, cockroaches and other pests, using fungal mycelia as both attractant and infectious agent.
2. Description of the Related Art
The use of chemical pesticides is the cause of many secondary environmental problems aside from the death of the targeted pest. Poisoning of soil and underlying aquifers may occur, along with pollution of surface waters as a result of runoff. Increases in cancer, allergies, immune disorders, neurological diseases and even death in agricultural workers and consumers have been attributable to the use of pesticides. Chemical pesticides are increasingly regulated and even banned as a health risk to citizens. Communities are increasingly in need of natural solutions to pest problems.
Compounding these problems, many pest type or vermin insects have developed a broad spectrum of resistance to chemical pesticides, resulting in few commercially available pesticides that are effective without thorough and repeated applications. In addition to being largely ineffective and difficult and costly to apply, chemical pesticides present the further disadvantage of detrimental effects on non-target species, resulting in secondary pest outbreaks. It is believed that widespread use of broad-spectrum insecticides often destroys or greatly hampers the natural enemies of pest species, and pest species reinfest the area faster than non-target species, thereby allowing and encouraging further pest outbreaks. There is therefore a particular need for natural alternatives.
Biological control agents have been tried with varying results. Bacteria such as Bacillus thurigenesis are used with some success as a spray on plants susceptible to infestation with certain insects. Fungal control agents are another promising group of insect pathogens suitable for use as biopesticides for the control of insects. However, limited availability, cost and reliability have hampered the development of such fungal control agents. Host range and specificity has been a problem as well as an advantage; a fungal pathogen that is virulent and pathogenic to one insect species may be ineffective against other species, even those of the same genus. However, some success has been demonstrated.
The typical lifecycle of a pathogenic fungi control agent involves adhesions of the spore(s) to the host insect cuticle, spore germination and penetration of the cuticle prior to growth in the hemocoel, death, saprophytic feeding and hyphal reemergence and sporulation. For example, U.S. Pat. No. 4,925,663 (1990) to Stimac discloses Beauveria bassiana used to control fire ants (Solenopsis). Rice, mycelia and spores (conidia) mixture may be applied to fire ants or used as a bait and carried down into the nest, thereby introducing spores. U.S. Pat. No. 4,942,030 (1990) to Osborne discloses control of whiteflies and other pests with Paecilomyces fumosoroseus Apopka spore conidia formulations. The Paecilomyces fungus is also useful for control of Diptera, Hymenoptera, Lepidoptera, Bemisia, Dialeurodes, Thrips, Spodoptera (beet army worm), Leptinotarsa (Colorado potato beetle), Lymantria (Gypsy moth), Tetranychus, Frankliniella, Echinothrips, Planococcus (Citrus mealybug) and Phenaococcus (Solanum mealybug). U.S. Pat. No. 5,165,929 (1992) to Howell discloses use of Rhizopus nigricans and other fungus in the order Mucorales as a fungal ant killer. U.S. Pat. No. 5,413,784 (1995) to Wright et al. discloses compositions and processes directed to the use of Beauveria bassana to control boll weevils, sweet potato whiteflies and cotton fleahoppers. U.S. Pat. No. 5,683,689 (1997) to Stimac et al. discloses conidial control of cockroaches, carpenter ants, and pharaoh ants using strains of Beauveria bassana grown on rice. U.S. Pat. No. 5,728,573 (1998) to Sugiura et al. discloses germinated fungi and rested spore termiticides of entomogenous fungus such as Beauveria brongniartii, Beauveria bassana, Beauveria amorpha, Metarhizium anisopliae and Verticillium lecanii for use against insects such as termites, cockroaches, ants, pill wood lice, sow bugs, large centipedes, and shield centipedes. U.S. Pat. No. 5,989,898 (1999) to Jin et al. is directed to packaged fungal conidia, particularly Metarhizium and Beauveria. The scientific journal literature also discusses similar uses of conidial preparations.
One disadvantage to such approaches is that the fungal lifecycle may be particularly sensitive to and dependent upon conditions of humidity, moisture and free water, particularly during the stages of germination, penetration of the cuticle prior to growth, and hyphal reemergence and sporulation after death of the insect.
Another continuing problem with existing techniques has been inconsistent bait acceptance. Baits are often bypassed and left uneaten. Such may be a particular problems with insects such as termites, as opposed to house ants and cockroaches, because it is usually not possible to remove competing food sources for termites. Attractants and feeding stimulants have sometimes increased the consistency of bait acceptance, but such increases cost and complexity, and there remains a continuing need for improved baits with improved bait acceptance.
A particular disadvantage with conidial fungal insect preparations becomes apparent from U.S. Pat. No. 5,595,746 (1997) to Milner et al. for termite control. Metarhizium anisopliae conidia are disclosed and claimed as a termite repellant in uninfested areas and as a termite control method in infested areas. The difficulties of utilizing conidia or conidia/mycelium as a bait and/or contact insecticide are readily apparent when considering that conidia are effective as an insect repellant to termites and are repellant in varying degrees to most or all targeted insect pests. A repellant, of course, does not facilitate use as a bait or contact insecticide. This may be a factor in explaining why fungal insecticides have all too often proven more effective in the laboratory, where conidia may be unavoidable in the testing chamber or even directly applied to insects, than in the field.
U.S. Pat. No. 4,363,798 (1982) to D""Orazio is for termite baits utilizing brown rot fungus as an attractant and toxicant boron compounds in mixtures effectively sufficient to kill termites without creating bait shyness. Brown-rot inoculated wood which is ground and mixed with cellulosic binder and boron compounds. Such an approach has the disadvantage of utilizing toxic boron compounds. In addition, the cultured mycelium must be further processed.
There is, therefore, a continuing need for enhancing the effectiveness of entomopathogenic (capable of causing insect disease) fungal products and methods. There is also a need for enhancing the attractiveness of such fungal pesticides to insects. There is also a need for improved packaging, shipping and delivery methods.
In view of the foregoing disadvantages inherent in the known types of fungal biocontrol agents, the present invention provides improved fungal biocontrol agents and methods of using such agents.
The present invention offers an environmentally benign approach to insect control by attracting the insects who ingest latent preconidial mycelium (which may be fresh, dried or freeze-dried) which then infects the host. The preconidial mycelium is both the attractant and the pathogenic agent. The infected insects carrying the fungal hyphae become a vector back to the central colony, further dispersing the fungal pathogen. Mycelium is grown in pure culture using standard fermentation techniques for in vitro propagation. The fermented mycelia is diluted and transferred into a sterilized grain or a mixture of sterilized grains. Once inoculated, the fermented mycelia matures to a state prior to conidia formation. The preconidial mycelium may be utilized as is or may be arrested in its development through flash chilling (or by other means such as air-drying or refrigeration) and packaged in spoilage-proof or sealed packages. The end-user facilitates opening the package and placing the exposed mycelia-grain contents in the vicinity of recent pest activity.
The present invention thus provides improved products and methods wherein the fungal mycelium acts as bait and attractant and as an ingested or food insecticide, palatable enough that insects will readily consume it even in the presence of competing food sources, with high recruitment of other insects among social insects that exhibit such behavior. This results in multiple visits to a highly attractive pathogenic bait, thereby providing effective individual insect and/or colony inoculation.
The present invention further provides these and other advantages with improved control of insect pests using fungal insecticidal compositions (mycopesticides) having strong attractant properties and placing these attractant mycopesticides in or around an object or area to be protected. The present invention also provides insecticidal baits which use, as a toxicant, relatively innocuous, naturally occurring materials as the active agent, so as to control insects without undue effect on the ecology. Finally, by actively avoiding the use of conidia, the time and expense of raising conidial stage mycelium and/or separating conidia is avoided.
Still further objects and advantages of the present invention will become more apparent from the following detailed description and appended claims.
Before explaining the disclosed embodiments of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the particular products and methods illustrated, since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation.